The cable of a device of this kind is stretched out along a dangerous installation so that the same can be stopped from anywhere along the cable, for example, by the cable being pulled up or down. It is generally desired that such devices, after an actuation, remain locked in an actuated state rather than recovering their normal condition. This prevents undetectable malicious actuation for simulating a breakdown in the installation. As a rule, therefore, the resetting means can be operated only by introducing a key into an appropriate lock.
However, it has been found that some commercially available equipment is not satisfactorily fraud-proof.